US3782959A

US3782959A - Polyhedral borane fogged direct-positive silver halide emulsion containing an organic sulfoxide

Info

Publication number: US3782959A
Application number: US00226513A
Authority: US
Inventors: J Bigelow
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1972-02-15
Filing date: 1972-02-15
Publication date: 1974-01-01
Anticipated expiration: 1991-01-01

Abstract

DIRECT POSITIVE PHOTOGRAPHIC SILVER HALIDE EMULSION ELEMENTS HAVING IMPROVED DEVELOPED SLVER COVERING POWER RESULTING IN INCREASED MAXIMUM DENSITY ARE PREPARED BY ADDING TO A CHEMICALLY FOGGED SILVR HALIDE EMULSION AT THE START OR DURING THE DIGESTION STEP FROM 50 TO 400 MILLILITERS OF A DIALKYL SULFOXIDE PER 1.5 MOLES OF SILVER NITRATE. THE ALKYL GROUPS OF THE SULFOXIDE MAY CONTAIN FROM 1 TO 4 CARBON ATOMS. THEE SILVER HALIDE EMULSIONS ARE PREFERABLY FOGGED WITH AMINE BORANES OR BORON HYDRIDES IN WHICH THE SKELETAL FRAMEWORK FORMS A POLYHEDRON BORANE CAGE CONTAINING 6 TO 12 BORON ATOMS OR A FRAGMENT THEREOF, THE WHICH MAY CONTAIN HETEROSKELETAL ATOMS SELECTED FROM THE GROUP CONSISTING CARBON, SULFUR AND NITROGEN ATOMS.

Description

fULs. c1. sis- 107 POLYHEDRAL -BORANE FOGGED DIRECT-POSI- TIVE SILVER HALIDE EMULSION CONTAINING AN ORGANIC SULFOXIDE John H. Bigelow, Rochester, N.Y., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del. No Drawing. Filed Feb. 15, 1972, Ser. No. 226,513 Int. Cl. G03c 1/28 15 Claims ABSTRACT on THE DISCLOSURE Direct positive photographic silver halide emulsion elements having improved developed silver covering power resulting in increased maximum density are prepared by adding to a chemically fogged silver halide emulsion at the start or during the digestion step from 50 to 400'milliliter's of a dialkyl sulfoxide per 1.5 moles of silver nitrate. The alkyl groups of the sulfoxide may contain from 1 to 4 carbon atoms. The silver halide emulsions are preferably fogged with amine boranes or boron hydrides in which the skeletal framework forms a polyhedron borane cage containing 6 to 12 boron atoms or a fragment thereof, and which may contain heteroskeletal atoms selected from the group consisting of carbon, sulfur and nitrogen atoms.

BACKGROUND OF THE INVENTION Field of the invention This invention. relates tordirect positive colloid silver halide photographic emulsions; more particularly it relates to such emulsions which are prefogged by a chemical fogging agent. Still more particularly, it relates to direct positive emulsions chemically fogged by borane compounds having increased developed silver covering power over the prior art direct positive elements.

Description of the prior art Direct positive emulsions are of course, well known and there are many diiferent methods of producing direct positive images. For example, a silver halide emulsionmay be given a short over-all exposure of high intensity radiation and then given a longer imagewise exposure of lower, intensity. Upon development, a direct positive will be obtained. Another method is to expose imagewise and develop and bleach out developed silver, flash' expose and then redevelop. A still further method is to use emulsion coated elements which have been chemicallyfogged with, for example, formaldehyde, hy-

idrazine, sodium arsenite, silver ions and other non-sulfide fogging agents thus eliminating a solarizing exposure. -Upon imagewise exposure and development of such Burt, U.S. Pat. 3,445,235. The Butt patent discloses and claims the use of rhodium and iridium salts in the direct positive emulsions described in the above Bigclow and Burtpatent as anti-kinking agents. The direct positive emulsions made as described in the Bigelow and Burt patents are quite fast as compared to direct positive elements of the prior art and avoid many of the disadvantages of long exposure times, low reversal densities, undesirable stain due to desensitizing dyes, as well as undesirable contrast, and a multiplicity of exposure steps United States Patent 3,782,959 Patented Jan. 1, 1974 SUMMARY OF THE INVENTION It has now been found that the developed silver covering power and maximum density of direct positive elements which have been chemically fogged, with at least one borane compound can be substantially increased by the addition of organic sulfoxides which can be represented by the following general formula:

wherein R and R are organic radicals which may be the same or different and may be various alkyl or aryl groups, e.g., methyl, ethyl, propyl, butyl, phenyl, tolyl,

etc. The borane compounds may be selected from the amine boranes, and borane compounds in which a skeletal framework forms a polyhedron cage or a fragment thereof, and which may contain heteroskeletal atoms selected from the group consisting of carbon, sulfur and nitrogen atoms.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Among the borane compounds which have been found useful as chemical sensitizers in this invention are the amine boranes disclosed in Bigelow and Burt, U.S. 3,361,- 564, e.g. morpholine borane, trimethylamine borane, etc., and boran hydride compounds in which the skeletal framework forms a polyhedron or a fragment thereof containing 6 to 12 boron atoms and may contain one or more heteroskeletal atoms such as carbon, sulfur and nitrogen. In other words, the useful compounds may be polyhedral homonuclear boranes of the series B H to B12H122 and the polyhedral heteronuclear boranes comprising the polyhedral azaboranes, polyhedral thiaboranes and polyhedral carboranes. These boranes and their preparation are described in The Chemistry of Boron and Its Compounds, E. L. Muetterties, John Wiley and Sons, New York, 1967 Polyhedral Boranes, by E. L. Muetterties and W. H. Knoth published by Marcel Dekker, Inc., New York, 1968 and numerous patents by the authors of the above publications.

While in general dialkyl sulfoxides wherein the alkyl groups containing 1 to 4 carbon atoms may be used it is preferred to use dimethyl or diethyl sulfoxide. The sulfoxides are preferably added in the amount of 50 to 400 milliliters per 1.5 moles of silver and at the beginning, during or at the end of the digestion period after the emulsion has been washed to remove the excess soluble salts resulting from the precipitation of the silver halides. They may be added separately or in admixture with the borane compounds and in the latter case the sulfoxide may be used as the solvent for the borane compound as a convenient means of adding it to the emulsion. The sulfoxides may be prepared by the methods disclosed in Smedslund, U.S. Pat. 2,702,824 and Goheen et al., U.S. Pat. 2,925,442.

For most efficient fogging action it is preferred that the borane compounds be added during the same stage as the sulfoxide compounds. The pH of the emulsion is adjusted to between 3.0 and 9.0 and preferably between 3.0 and 7.0 and maintained at a pre-selected level in this range during digestion. After digestion, the pH is adjusted to the desired coating pH and the conventional coating aids are added. Coating aids such as saponin, sodium salts of polyether sulfonates, alkyl sulfonates, cetyl betaine, etc., can be utilized. The emulsion is then coated and dried in the manner known to those skilled in photographic manufacturing methods.

The sensitometric characteristics of the direct positive emulsions may be determined by exposing in an intensity scale sensitometer (described on p. 616, Mees, The Theory of the Photographic Process, MacMillan Company, New York (1942)) using a suitable step wedge and light intensity depending upon the inherent speed of the emulsion. Direct positive emulsions are of course tailored to meet certain needs in the industry and are manufactured accordingly. After exposure in the sensitometer the strips are developed in suitable developers as shown below, immersed in a short stop, fixed in a conventional fixer, washed and dried. In evaluation of the processed strips, the maximum density is the highest density value obtained on the image of the step wedge and can be Developer I (high contrast type):

Water m1 500 Sodium sulfite (anhydrous) grams 30.0 Paraformaldehyde do 7.5 Potassium metabisulfite d 2.5 Boric acid (crystals) do.. 7.5 Hydroquinone do 22.5 Potassium bromide do 1.5 Water to make 1.0 liter.

Developer II (continuous tone type):

Water ml 500 N-methyl-p-aminophenol sulfate grams 1.0 Sodium sulfite (anhydrous) ..do 15.0 Hydroquinone do 4.0 Sodium carbonate (monohydrate) do.. 26.5 Benzotriazole d0.. 0.1 Potassium bromide do.. 0.6

'Water to make 1.0 liter. Sensitometric evaluation adduced the following data:

Amount of dimethyl sulfoxide per 1.5 Coating Maximum density Borane compound mole/1.5 moles moles weight, mg.

AgNOa AgNOg, ml. AgNQs/t't. Dev. I Dev. II

Morpholino borane 4. 8 1O 1 None 512 3.61 3. 71 0518 11123.-. 3. 6X10- 1 None 861 4.17 4. 25 CSB9H zS 0.9 10 1 None 615 4. 45 4.55 CSBQHIQS 4. 5X10- 1 None 850 4. 35 4. 25 Morpholine borane 4. 8X10- 360 444 3. 87 4. 85 C H BHHNS 3. 6X16 360 709 5. 99 6. 85 CQHjfiBllHlOS 2X10 200 779 6. 73 6. 85 OGHsBllHlOS 1 10- 100 619 5. 63 5. 45 (CIIs)4NB1oHu 3. 6Xl0' 360 726 6. 65 6.85 (CH3)4NB10H11S ZXIO- 200 674 7. 15 7.05 (CHshNBioHnS- 1 10- 160 657 6. 05 6.13 CSBpHlzS 0. 9X10 120 l, 301 6. 85 7. 15+ CSBQHUS 3. 6X10 360 840 7. 15+ 7. 15+

1 Control.

consldered a measure of the effect of the addition of the EXAMPLE II sulfoxide compound to the system.

The invention will now be illustrated in and by the following examples:

EXAMPLE I A direct positive emulsion was made in the following manner. To an aqueous solution of gelatin containing 1 mole of potassium chloride and 6.8 mole of rhodium trichloride, there was rapidly added 1 mole of silver nitrate in an aqueous solution. To the resulting mixture there was added 0.4 mole of potassium bromide in aqueous solution and the resulting emulsion was then ripened by heating for 10 minutes at 160 F. A second portion of 0.6 mole of potassium bromide was added and the emulsion further ripened 10 minutes at 160 F. The resulting emulsion was then cooled, washed and redispersed in the manner disclosed in Moede, U.S. Pat. 2,772,- 165, issued Nov. 27, 1956.

The aqueous gelatin solution was added to the redispersed emulsion to provide a gelatin content of about 7 to 8%. The pH was adjusted to 8.2 and borane compounds and dimethyl sulfoxide were added to separate portions of the emulsion in the quantities indicated in the following table. The emulsions were stirred and digested for 40 minutes at 130 F. The emulsions were cooled to 95 F. and the pH adjusted to 7.0 with acetic acid and a wetting agent, i.e., saponin, was added. The viscosity was suitably adjusted and the emulsion was coated at approximately 700 mg. AgNO per square foot on a photographic film support and dried in a conventional manner. Sensitometric strips were exposed in the above described sensitometer with a quartz-I lamp, /3 wedge, and luxometer units. The strips were developed in the two following developers, 3 minutes in the developer I and 1.5 minutes in developer II.

A direct positive emulsion was made as described in Example I up to and through the washing and redispersion steps. The temperature of the redispersed emulsion was raised to 130 F. and there was added an aqueous solution of gelatin to give a final concentration of 7 to 8% gelatin. The pH was adjusted to 7.0 and 4.0 10- mole of the borane compound CsB H S and 7.4 10- mole of hydrochlorauric acid (HAuCl per 1.5 moles of silver nitrate was added. The emulsion was divided into two portions the quantities of dimethyl sulfoxide as indicated in the table 'below. The emulsions were digested for 40 minutes at 130 F. and cooled to F. The usual coating aids, e.g. wetting agents, emulsion hardeners, etc. were added and the emulsions were coated on photographic quality film base and dried in a conventional manner. Strips of the exposed emulsion elements were exposed in the intensity scale sensitometer referred to above using a #3 lamp, SQRTZ wedge Ser. No. 8,876,418 for 16 seconds. The strips were processed as described in Example I and gave the following data:

Maximum density Amount of dimethyl sulioXide/LB AgNOa Dev. I Dev. II

while others, particularly the amine boranes operate more effectively above 7 and preferably 8.0 to 9.0.

As is evident from the sensitometric data, the use of dialkyl sulfoxides with the borane fogging agents increases the maximum density of the direct positive elements. The elements of this invention, as shown in the examples, may be developed in any standard developing solution either of the continuous tone type or the high contrast lithographic type using standard techniques. Variations in the developing solution will have much the same eifect as it would in developing non-reversal emulsions. No pre-exposure operations or auxiliary processing procedures are necessary or desired in using the novel elements of this invention. It is also unnecessary to utilize stain producing non-sensitizing dyes or other desensitizing compounds in the emulsion. The borane compounds are far superior to formaldehyde, the principal fogging agent of the prior art, because the boranes do not have a hardening effect on the gelatin layer.

The silver halide emulsions of this invention can be made with any of the macromolecular, water-permeable colloids known to be suitable for the purpose of acting as a colloid carrier for silver halide grains. In addition to gelatin, there may be used polyvinyl alcohol and its derivatives, e.g., partially hydrolyzed polyvinyl acetates, ethers and acetals, hydrolyzed interpolymers of vinyl acetate and unsaturated addition polymerizable compounds such as maleic anhydride, acrylic and methacrylic acid esters, poly-N-vinyllactams, polysaccharides, e.g., dextran, dextrin, etc., the hydrophilic copolymers disclosed in Shacklett US. 2,833,650, hydrophilic cellulose ethers and esters, and acrylamide polymers. Mixtures of these binders can also be used as well as water-permeable binding agents containing dispersed polymerized vinyl compounds such as those disclosed in Nottorf US. Pat. 3,142,568 issued July 28, 1964.

The emulsions of this invention may be coated on any suitable support including photographic quality paper and transparent film. For example, the cellulosic supports, e.g., cellulose acetate, cellulose triacetate, cellulose mixed esters, etc., may be used. Polymerized vinyl compounds, e.g., copolymerized vinyl acetate and vinyl chloride, polystyrene and polymerized acrylates may also be mentioned. The film formed from the polyesters made according to the teachings of Alles, US. Pat. 2,779,684 and the patents referred to in the specification of that patent. Other suitable supports are the polyethylene terephthalate/isophthalates of British Pat. No. 766,290 and Canadian Pat. 562,672 and those obtainable by condensing terephthalic acid and dimethyl terephthalate with propylene glycol, dimethylene glycol, tetramethylene glycol or cyclohexane-1,4-dimethanol(hexahydro-pxylene alcohol). The films of Bauer et al., U.S. Pat. 3,059,543 may also be used. The above polyester films are particularly suitable because of their dimensional stability. The emulsions are generally coated on the supports to give a coating weight equivalent to about 700 mg./ft.

Many borane compounds other than those referred to above can be used as chemical fogging agents for the direct positive photographic elements of this emulsion in accordance with this invention.

What is claimed is:

1. A direct-positive, water-permeable colloid-silver halide emulsion containing a fogging amount of a borane and an organic sulfoxide of the formula wherein R and R are phenyl and tolyl and alkyl radicals containing 1 to 4 carbon atoms, said borane being selected from the group consisting of the amine boranes and the boron hydrides, said amine boranes and boron hydrides having a polyhedral skeletal framework which has from 6 to 12 carbon atoms and may contain heteroskeletal atoms selected from the group consisting of carbon, sulfur and nitrogen.

2. An emulsion according to claim 1 wherein said organic sulfoxide is dimethyl or diethyl sulfoxide.

3. An emulsion according to claim 1 wherein said organic sulfoxide is present in an amount of 50 to 400 milliliters per 1.5 moles of silver.

4. An emulsion according to claim 3 containing rhodium chloride.

5. An emulsion according to claim 3 wherein the silver halide is a silver chlorobromide emulsion.

6. An emulsion according to claim 3 wherein the silver halide is a silver bromochloride emulsion.

7. An emulsion according to claim 3 wherein the colloid is gelatin.

8. An emulsion according to claim 3 wherein said boron hydride is a polyhedral homonuclear borane of the series B6H6 2 t0 B zHlg 9. An emulsion according to claim 3 containing a gold compound.

10. An emulsion according to claim 3 having a pH of about 3.0 to 9.0.

11. A photographic element comprising a support bearing a layer of an emulsion as defined in claim 1.

12. An element according to claim 10 wherein said organic sulfoxide is dimethyl or diethyl sulfoxide.

13. An element according to claim 11 wherein said organic sulfoxide is present in an amount of 50 to 400 milliliters per 1.5 moles of silver.

14. An element according to claim 13 containing rhodium chloride.

15. An element according to claim 12 containing a gold compound.

References Cited UNITED STATES PATENTS 3,219,450 11/1965 Goldberg 96-107 3,607,288 9/1971 Burt 96-64 NORMAN G. TORCHIN, Primary Examiner W. H. LOUIE, JR., Assistant Examiner US. Cl. X.R. 96l08